Process for the manufacture of a metallized article

Abstract: It is possible to manufacture articles out of thermoplastic materials and to metallize the articles at their surface. In this way one can manufacture reflectors and similar articles. Most thermoplastic materials require extra processing steps prior to the metallization like application of primers, chemical etching and the like. The invention is based on the discovery that a certain type of materials can be metallized without any extra processing steps. The materials involved are polyestercarbonates or blends of polyestercarbonates and polycarbonate. This is quite surprising since polycarbonates can not be metallized in good quality without extra processing steps prior to the metallization step.

Description: The invention relates to a process for the manufacture of a metallized article out of a thermoplastic material. It is generally known to mold objects out of thermoplastic materials and to metallize the obtained objects completely or partly at their surface. To obtain a good adhesion between the thermoplastic material and the metal layer it is usually required to incorporate in the thermoplastic materials additives. Alternatively it is possible to subject the surface to be metallized to a pretreatment prior to the actual metallization step. In some applications like mirrors and reflectors for the automotive industry aromatic polycarbonates are a preferred thermoplastic material. Unfortunately it is not possible to metallize objects made out of polycarbonate without taking certain extra precautions as indicated above. It has now surprisingly been found that materials very similar to polycarbonate's can be directlv metallized. According to the invention an article is molded out of a material based on a blend of an aromatic polycarbonate and polyestercarbonate with at least 10 mol % of ester bonds calculated with respect to the total of ester bonds and carbonate bonds, not comprising additives for improving the adhesion between the thermoplastic material and the metal layer and wherein the formed article is metallized without subjecting the formed article to a pretreatment for improving the adhesion between the thermoplastic material and the adhesive layer. EP-A 0 245 691 describes foils made out of polycondensates. The polycondenstate can consist by way of example of blends of polyester and aromatic polyestercarbonates, blends of aromatic polycarbonates and aromatic polyester and aromatic polyestercarbonates, a blend of different polyestercarbonates. Most preferred are polycarbonates as obtained in the synthesis. It is stated that the foils give good metal adhesion. There are no specific examples for metallized foils. EP-A 0 245 689 describes the use of the foils of EP-A 0 245 691 for making printing ribbons. It is indicated that carbon or graphite comprising compositions show a good adhesion for metals such as aluminum. There are however no specific examples for metallized foils. DE-A 37 26 189 describes spectacle frames made out of aromatic polyestercarbonates. It is stated that the frames can be metallized. There are no specific examples of metallized frames. The articles of the invention can be obtained by conventional processes for molding thermoplastic materials like extrusion and injection molding. After the molding step the obtained objects can be metallized by conventional metallization processes like vacuum deposition or sputtering. Aluminium is the preferred metal. A pretreatment of the surface to be metallized is however not required. The incorporation of special additives is not required either. As stated above the articles are made out of a blend of a polyestercarbonate and an aromatic polycarbonate. The blend of the polyestercarbonate and the polycarbonate can be admixed with usual additives as long as the additives do not disturb the adhesion between the metal layer and the thermoplastic material. Polyestercarbonates and aromatic polycarbonates are generally known materials which are readily available. Suitable polyestercarbonates can be obtained by an esterification reaction of a carbonate precursor such as phosgene or diphenylcarbonate, a diphenol such as bisphenol A and an ester precursor such as a difunctional carboxylic acid such as terephthalic acid or an ester forming derivative thereof. Polyestercarbonates have ester bonds and carbonate bonds in their polymer chain. Suitable polyestercarbonates have been described in US 3,169,121. A process for the preparation of suitable polyestercarbonates can be found in US 4,238,596 and US 4,238,597. The ester bonds can also be derived from aliphatic dicarboxylic acids or mixtures of aliphatic and aromatic dicarboxylic acids. In this context a reference can be made to US-A-4,983,706 and US-A-5,025,081. In the blend of the polyestercarbonate and the polycarbonate the minimum content of ester bonds is 10 mol%. This has been calculated with respect to the total number of ester bonds plus carbonate bonds; the number of carbonate bonds is taken together from the polyestercarbonate plus the polycarbonate. Aromatic polycarbonates are generally prepared by reacting a dihydric phenol compound with a carbonate precursor, for example, phosgene, a halogen formate or a carbonate ester. Aromatic polycarbonates are polymers which comprise units of the formula wherein A is a bivalent aromatic radical which is derived from the dihydric phenol used in the preparation of the polymer. Dihydric phenols which may be used in the preparation of the aromatic polycarbonates are mononuclear or polynuclear aromatic compounds which comprise two hydroxy radicals each directly bonded to a carbon atom of an aromatic nucleus. Said dihydride phenols may be substituted with one or more halogen atoms or one or more alkylgroups. Branched polycarbonates known per se, as described, for example in US-S-4,001,184, are also suitable. The blend of the aromatic polycarbonate and the polyestercarbonate can be prepared by conventional processes like melt blending compounding in an extruder. The invention will be illustrated by the following examples. Examples The following materials have been used in the examples: Polyestercarbonate: a polyestercarbonate in the form of pellets derived from bisphenol A, terephthaloylchloride and isophthaloylchloride. The overall composition was as follows: 80% ester bonds (8% from terephthaloylchloride and 72% from isophthaloylchloride) and 20% carbonate bonds. The polyester carbonate had an IV of 51 ml/g as measured in MeCl 2 at 25 degrees C. Aromatic polycarbonate: an polycarbonate homopolymer in the form of pellets derived from phosgene and bisphenol A with an intrinsic viscosity of 52 ml/g as measured in MeCl 2 at a temperature of 25 degrees C. For the examples were a blend of the polyestercarbonate and the polycarbonate was used the blend was prepared by compounding the materials in the indicated quantities in an extruder with an average temperature setting of 300 degrees C. The extrudate was pelletized. Of each of the different compositions indicated below discs were made by a conventional injection molding process. The discs as obtained from the molding process were metallized by vacuum deposition of aluminium. The adhesion of the metal layer was tested as follows. With a cross hatch knife a grid is cut through the metallization layer. An adhesive tape was pressed by hand upon the metallized side of the disc. After 0.5 minutes the tape was torn off the surface by hand. The percentage of the surface which remained properly metallized was determined; the higher this percentage is the better the adhesion between the metal layer and the thermoplastic substrate. The tested compositions and the measured results are given here below in Table A. Composition Adhesion test result remaining percentage of metal layer -100% by weight polyestercarbonate more than 95 -60% by weight polyestercarbonate + 40 % by weight polycarbonate about 90 -40% by weight polyestercarbonate + 60 % by weight polycarbonate about 80 -20% by weight polyestercarbonate + 80 % by weight polycarbonate about 65 -pure polycarbonate less than 50 As can be seen from the results of the table, articles made out of pure polycarbonate show a very bad result. Addition of relative small amounts of polyestercarbonate (as little as 20 % by weight resulting in an ester bond content of 16 mol%)results in a remarkable increase in the adhesion.

Claims: Process for the manufacture of a metallized article out of a thermoplastic material wherein an article is molded out of a material based on a blend of an aromatic polycarbonate and polyestercarbonate with at least 10 mol % of ester bonds calculated with respect to the total of ester bonds and carbonate bonds, not comprising additives for improving the adhesion between the thermoplastic material and the metal layer and wherein the formed article is metallized without subjecting the formed article to a pretreatment for improving the adhesion between the thermoplastic material and the adhesive layer. Process according to claim 1, wherein the article is partially metallized. Process according to claims 1 - 2, wherein the article is metallized with an aluminum layer.

Inventors: DE JONG ROBERTUS E, FONTANA LUCA P, GRIMM MICHAEL B, MAAS CHRISTIANUS J J, DE JONG, ROBERTUS E., FONTANA, LUCA P., GRIMM, MICHAEL B., MAAS, CHRISTIANUS J. J.
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 1994
Main classification: C23C14
IPC codes: C08L69, B32B15, C08G64, C08G63, C23C14